Influence of improvement practices on big blue-stem and indiangrass seed production in tallgrass prairies

Published source details Masters R.A., Mitchell R.B., Vogel K.P. & Waller S.S. (1993) Influence of improvement practices on big blue-stem and indiangrass seed production in tallgrass prairies. Journal of Range Management, 46, 183-188.
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Summary

In North America some species of native prairie grasses are suitable for revegetating degraded rangelands and marginal cropland if seed can be produced in bulk. In this study, the effect of spring burning, fertilization, and atrazine (a widely used herbicide used to kill broadleaf and grassy weeds) on big bluestem Andropogon gerardii gerardii and indiangrass Sorghastrum nutans reproductive stem density and seed production was determined in nine tallgrass prairies near the cities of Bloomfield and Lincoln, and Virginia village (Nebraska, central USA), from 1987 to 1990.

The study grasses were selected as they are common in most tallgrass prairies. The prairies used here were deemed in good to excellent condition (as indicated by botanical composition).

Individual treatments and treatment combinations were applied (with untreated controls for comparison). Plots (typically 10’s of metres-square) assigned for burning were burned during March to mid-May. Atrazine was applied at rates of 0 and 2.2 kg a.i./ha in mid-spring. Fertilizer was applied in late spring at 0 and 110-0 kg N-P/ha at Lincoln in 1987, 0 and 110-22 kg N-P/ha at Bloomfield in 1987 and all sites in 1988, and 0 and 67-22 N-P kg/ha at all sites in 1989 and 1990.

Within treatment plots and controls, bluestem and indiangrass reproductive stem density and seed production were assessed in the year of treatment application. Seed samples were collected and the number of germinable seeds produced per metre-square calculated. Density of stems with inflorescences was assessed by counts within 0.5 m² quadrats.

Reproductive stem density response to treatments varied by species and environment. Treatment (individual or combinations) increased stem density of big bluestem in five of nine environments and indiangrass in four.

No single treatment or treatment combination consistently increased seed production and the overall quantity produced was considered low. The amount of germinable seed produced was positively influenced by treatments only in 1987 and 1990 when precipitation was above or near the long-term average:

In 1987 at Bloomfield, in atrazine plots indiangrass germinable seed was 481 seeds/m², compared to 202/m² produced in untreated controls. In 1987 at Lincoln, in fire + fertilizer + atrazine combined plots germinable indiangrass seed was 2,517 seeds/m², compared to 331/m² in the controls. In 1990, burning in mid-May increased big bluestem seed number from 52 to125 germinable seeds/m² at Virginia, and fertilizer increased big bluestem seed number from 333 to 724 seeds/m² at Lincoln.

Germinable seed was not produced in 1988 and 1989, presumably because of drought.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume46/Number2/